The present invention relates to an apparatus for controlling the operation of a hydraulic machine of the type having a plurality of runners mounted on a common shaft and movable flow-rate adjusting vanes provided around respective runners. More particularly, the invention is concerned with an apparatus for controlling the operation of a hydraulic machine of the type mentioned above in such a manner as to control the opening of the flow-rate adjusting vanes to provide a constant output of the machine.
Generally, hydraulic machines are intended for utilization of potential energy and kinetic energy of water or to send the water to a place demanding the water supply. Typical examples of such hydraulic machines are water wheels in hydraulic power station and pumps.
Pumping-up power stations are becoming popular in order to meet the peak of demand for electric power. The head of the pumping-up water stations built in recent years is becoming greater, which in turn gives a rise to a demand for multi-stage turbines. The multi-stage pump turbine consists of a plurality of pump turbines, i.e. a plurality of runners mounted on a common shaft and movable flow-rate adjusting vanes (referred to as guide vanes, hereinunder) disposed around respective runners.
The plurality of runners of the multi-stage pump turbine are so designed as to share equal or proportional parts of the total head or lift. Thus such multi-stage pump turbine is designed such that a flow rate-head (or lift) characteristics at each stage are equal to one another or are related to one another in predetermined ratios.
In the operation of the multi-stage pump turbine, it is necessary that the guide vanes of all stages are controlled in synchronism such that each runner shares an equal or a proportional part of the total head.
The conventional apparatus for controlling the operation of this multi-stage pump turbine includes two governors when the number of stages is two, and three governors when the number of stages is three, in contrast to the controlling apparatus for a single-stage machine which requires only one governor. In this conventional control apparatus having a plurality of governors, the respective governors separately receive the revolving speed signal from a generator motor connected to the multi-stage pump. As a matter of fact, however, a slight fluctuation in performances of the governors is inevitable mainly for the reasons related to the production. It is, therefore, extremely difficult to attain a perfect synchronization of opening and closing operation of guide vanes of all stages. The use of a plurality of governors for a single multi-stage pump turbine raises the production cost and, in addition, impractically complicates the control system due to an increase of the number of the controlled elements, to deteriorate the reliability seriously.
On the other hand, it has been attempted to control the guide vanes of all stages by a single governor. This attempt, however, cannot make the stages share proportional parts of total head while it can be suitably applied to the control in which the stages share equal parts of the total head.